1. Technical Field
The present invention relates to a coating composition for semiconductor device fabrication, a method of forming a mask pattern, and a method of fabricating a semiconductor device; more particularly, a mask pattern for semiconductor device fabrication, having a fine pattern beyond a wavelength limit of lithography, a method of forming the mask pattern, a coating composition for fine pattern formation, and a method of fabricating a finely patterned semiconductor device using the coating composition.
2. Discussion of Related Art
In a conventional patterning process for semiconductor device fabrication, a photoresist pattern is formed on a certain film to be etched for pattern formation. The certain film such as a silicon film, a dielectric film, or a conductive film, is etched using the photoresist pattern as an etching mask to form a pattern. With the increase of integration of semiconductor devices, the design rule of smaller critical dimension (CD) and lithography technology of forming fine patterns become critical. The fine patterns include contact holes having a smaller opening size or spaces having a smaller width.
In a conventional lithography technology for forming smaller size contact holes, a short-wavelength exposure tool such as an E-beam lithography or a half-tone phase shift mask is used. The short-wavelength exposure tool based lithography is material dependent and uneconomical. The half-tone phase shift mask based lithography is difficult to form contact holes which are less than 150 nm in size.
Various technologies for forming a fine pattern have been suggested. Japanese Patent Publication No. 1989-307228 discloses a technology of forming a resist pattern. A resist pattern formed by exposure and development of a resist film is thermally treated so that the profile shape of the resist pattern is changed. According to this technology, a resist flow rate is different in an upper area and a middle area of the resist pattern. When the CD shrinkage of the resist pattern by thermal flow is 100 nm or more, the profile of the resist pattern is transformed by rapid flow characteristics of the resist film. As a result, a bowing profile is obtained near the middle area. This technology has a limitation in adjusting the flow rate of the resist pattern, which makes it difficult to reduce the CD of the resist pattern while maintaining a vertical profile shape.
Japanese Patent Publication Nos. 1993-241348, 1994-250379, 1998-73927, 1999-204399, 1999-283905, 1999-283910, 2000-58506, 2000-298356, 2001-66782, 2001-228616, 2001-19860, and 2001-109165 disclose a method of forming a resist pattern by a chemical treatment. Japanese Patent Publication No. 2001-228616 discloses a technology of decreasing a hole diameter and an isolation width of a resist pattern by increasing the thickness of the resist pattern. According to this technology, the resist pattern that can serve as an acid donor is coated with a framing material to be cross-linked with the acid. When the acid is transferred from the resist pattern to a layer made of the framing material by heating, a cross-linked layer is formed as a layer covering the resist pattern at an interface between the resist pattern and the framing material layer. However, a chemical cross-linking reaction may also occur at an unwanted area, thereby causing pattern defects. With conventional technology, a precise temperature control to induce a desired chemical cross-linking reaction may be difficult.
Japanese Patent Publication Nos. 2003-107752, 2003-84448, 2003-84459, 2003-84460, 2003-142381, 2003-195527, 2003-202679, 2003-303757, and 2003-316026 disclose a composition for pattern formation and a pattern formation method. Japanese Patent Publication No. 2003-202679 discloses a method of forming patterns using a coating agent. The coating agent is coated on a substrate having photoresist patterns to decrease space between the photoresist patterns by thermal shrinkage effect of the coating agent. Since the thermal shrinkage amount of the coating agent typically depends on the temperature profile of the substrate, it may be difficult to form uniform resist patterns on the whole surface of the substrate. Furthermore, a resist material with a low glass transition temperature needs to be used. In addition, to accurately obtain a certain feature size, a complicated calculation process for correction of iso-dense bias needs to be done.
As described above, among CD reduction technologies that have been suggested hitherto, a resist flow technology by thermal treatment may not provide a good sidewall profile. For example, coating of a separate material on a resist pattern may induce an unwanted cross-linkage in the resist pattern, thereby causing pattern defects. Furthermore, the material remained on an unwanted region may cause various pattern defects after development. When an exposure tool with a wavelength of about 157 nm or about 193 nm is used or when the sizes of holes or trenches to be formed decrease, pattern defects may increase.
In a conventional bi-layer resist (BLR) or multi-layer resist (MLR) process, patterning is performed by photolithography using a silicon-containing resist as a top layer resist. A silicon atom in the silicon-containing resist is converted into glass (i.e., SiOx) by a dry etching method using O2 reactive ion etching (RIE) technology to form a cured layer on a surface of a resist layer. The cured layer formed serves as an etching mask in a subsequent dry etching process. Since the cured layer increases a resistance to the dry etching, a pattern with a high aspect ratio can be formed and a pattern falling phenomenon can be prevented. Thus, a patterning process based on MLR can provide a high-resolution pattern with a high aspect ratio. However, as the content of silicon in a top resist material increases, a top resist layer has poor thermal stability and wettability to a developer.
Furthermore, when a resist flow technology by thermal treatment is applied to a resist pattern made of the top resist material to form a fine pattern, the thickness of the resist pattern decreases, which renders pattern transfer to a bottom resist layer difficult. When a technology of forming a fine pattern using a cross-linked layer as a layer covering a resist pattern is applied to a MLR process, a material used for cross-linkage in a surface of the resist pattern may have insufficient silicon contents. Thus, the cross-linked layer cannot serve as a hard mask during a dry etching by O2 RIE technology. Japanese Patent Publication No. 1999-283910 discloses a silicon-containing resist material. However, this technology involves rinsing with a mixed solution of an organic solvent instead of deionized water, which renders mass production difficult.